Non-woven fiber batt has a demonstrated usefulness in a wide variety of applications. This material has been used in manufacturing scouring pads, filters, and the like, but is particularly useful as a filler material in various personal comfort items such as stuffing in furniture, mattresses and pillows, and as a filler and insulation in comforters and other coverings. One of the inherent characteristics of fiber batt is its cushioning ability due to the large amount of air space held within the batt material. The air space defined within the fiber batt acts as a thermal insulation layer, and its ready displaceability allows support in furniture, mattresses and pillows.
Typically, the fiber batt is produced from a physical mixture of various polymeric fibers. The methods for manufacturing the batt are well known to those skilled in the art. Generally, this method comprises reducing a fiber bale to its individual separated fibers via a picker, which “fluffs” the fibers. The picked fibers are homogeneously mixed with other separated fibers to create a matrix which has a very low density. A garnet machine then cards the fiber mixture into layers to achieve the desired weight and/or density. Density may be further increased by piercing the matrix with a plurality of needles to drive a portion of the retained air therefrom.
A resilient structure such as a seat, a furniture back or a sleeping surface must be able to support a given load, yet have sufficient resilience, or give, to provide a degree of comfort. For these structures, a heat bonded, low melt fiber batt may be used to form an inner core, or as a covering. To provide the necessary support, a certain fiber density must be built into the fiber batt. If the fiber density is too high, the seat cushion or mattress will have sufficient rigidity but it will be too firm. If the fiber mass is less dense, it will be more comfortable. However, it will not be as durable and will be more susceptible to flattening out after use. Thus, while fiber batting has a number of well-recognized advantages, it is difficult to achieve a high degree of structural support and/or comfort for a resilient structure with a covering or core made from a heat bonded low melt fiber batt.
To minimize these limitations, it is common to combine a fiber batt with an interconnected wire lattice. For instance, mattresses often include a wire lattice sandwiched between two layers of fiber batting. The wire lattice provides a high degree of structural rigidity. Resiliency can be built into the wire lattice by including coil or leaf springs at various locations. To do this, the lattice may include a plurality of internal coils interconnected by border wire and anchoring springs. While a resilient structure with an interconnected wire lattice of this type has many desirable features, it requires a relatively large quantity of steel. Moreover, its manufacture and construction also requires relatively complex machinery to form and interconnect the steel. The overall cost of a typical resilient mattress of this type reflects the relatively high quantity of steel used to make the support lattice and the complexity of the required machinery.
An alternative construction is known which does not have the disadvantages of the above wire lattice. With the alternative construction, a heat bonded, low melt, fiber batt is initially formed. Thereafter, heated coil springs are screwed through the thickness of the heat bonded, low melt, fiber batt at predetermined positions. The heated coil springs melt some or all of the immediately surrounding low melt fibers. As the melted fibers resolidify or cure, they interlock with the coil springs to hold and encapsulate the coil springs in place within the fiber batt. The fiber batt may be compressed after insertion of the springs, or while the springs are still hot, and until curing is completed.
If the coil springs are unknotted and have a constant diameter throughout their length, threading the coils through the thickness of the fiber batt from a top or bottom surface presents minimal breakage and disruption to the fiber strands. Each successive turn travels along substantially the same path as a prior turn, so that fiber strand damage in the fiber batt is minimal. However, as the heated coil spring is threaded through the fiber batt, the leading turn of the coil spring quickly cools and will cool below the melt temperature of the fiber strands before it is threaded completely through the thickness of the fiber batt. In that event, fiber strands resolidify on the cooled coil; and as the threaded insertion of the coil continues, the solidified fiber strands thereon tear away from their adjacent fiber strands. That process diminishes the integrity of the fiber batt at the location of the tear, and further, any fiber strand tearing prohibits the coil spring from interlocking with its immediately surrounding fiber strands.
The known coil threading process has another significant disadvantage. In some applications, it is desirable to use coil springs having turns of different diameters over the length of the coil spring. However, as the variable diameter coil spring is threaded through the thickness of the fiber batt, a smaller diameter turn cannot travel along the same path as a larger diameter turn. Therefore, variable diameter coil springs cannot practically be threaded through the thickness of the fiber batt.
In other applications, it may be desirable to use coil springs in which the ends of a coil are knotted to the end turns. With such a coil, threading of the coil through the fiber batt is not possible. Therefore, for all practical purposes, knotted coil springs cannot be used.
It is also known to cut a plurality of intersecting slit patterns in the fiber batt, from one side thereof. Preferably, each intersecting slit pattern has two slits which define a cross shape. The springs are then inserted into the slit patterns until the endmost turns of the springs lie flush with or slightly above the top and bottom surfaces of the batt. Preferably, variable diameter, knotted type springs are used, and the wedge-shaped segments of fiber batt created by the cross-shaped slits fill in between the turns of each spring to interlock the spring in the batt without the necessity of heating and cooling the batt and/or spring. However, heat and compression and/or heating, cooling and compression may be applied to the fiber batt, as described previously, before or after the additional layers are placed on the batt.
The above described embodiment of inserting a coil spring into a slit in the fiber batt also has disadvantages. First, cutting slits through the thickness of the fiber batt cuts a substantial number of fiber strands through the thickness; and as described above, substantially weakens the resiliency and load carrying capability of the fiber batt. The process of slitting the fiber batt requires extra tooling and a processing station as part of the manufacturing process. That tooling and processing station also requires maintenance; and therefore, they add significant cost to the manufacturing process.
Thus, the known processes of threading a coil spring through a fiber batt and slitting a fiber batt for coil insertion have significant limitations and disadvantages. Therefore, there is a need to provide a resilient structure in which coil springs are inserted into a fiber batt without the above disadvantages.